Abstract:The gas-phase. flameJess oxidation of chlorobenzcne (C 6H sCI) was studied experimentally in a 2. J cm 10 quartz flow-reactor operating at I atm pressure. Temperatures investigated were in the range 630-850°C, reaction times in the range 0.4-1.94 s, O 2 concentrations in the range 1.8-3.3% (fuel rich) at a fixed C, HsCI concentration of about 0.5% in Arcarrier gas. The absolute concentrations of the reactants and the products CO,
“…This is consistent with the first-order pyrolysis model proposed by De Vissher et al for monocyclic aromatic compounds (). In addition, products characteristic of the reaction (carbon monoxide, carbon dioxide, acetylene, HCl) are gases obtained experimentally in gas-phase flameless oxidation of chlorobenzene ( , ). 5 4-ClPh, ClBz, and Cl - evolution with time.…”
Propagation of an ultrasonic wave in a water generates the cavitation bubbles, which behaving like microreactors are the center of a high-energy phenomenon leading to destruction of organic pollutants. In this work, a comparative study conducted with chlorobenzene and 4-chlorophenol as models for hydrophobic and hydrophilic substrates, respectively, clearly shows the two sites where the sonochemical reactions can occur. As ultrasonic frequency may alter noticeably the reaction rates, the experiments were conducted at 20 and 500 kHz. The dechlorination yields were found to be higher with the 500-kHz ultrasonic source than with the common 20-kHz probe. For chlorobenzene (ClBz), the reaction proceeds expeditiously, chlorine is quantitatively recovered as chloride ions, and 44% of the carbon atoms are recovered as CO and CO 2 . The rate of disappearance of starting material, Clrelease, and intermediate and final products provide some evidence of a reaction occurring thermally inside the cavitation bubble. 4-Chlorophenol (4-ClPh) degradation occurs at a lower rate. Clrelease and formation of hydroxylated intermediates are evidence of a two-step reaction involving the • OH radical outside the cavitation bubble. The consequences are important for water containing both 4-ClPh (0.5 mM) and ClBz (0.5 mM). ClBz degrades first; 4-ClPh transformation starts only when ClBz concentration reaches a low level (0.02 mM). The sonochemical treatment appears to be particularly efficient for the destruction of volatile chloroaromatic hydrocarbons (1,2-dichlorobenzene, 1,3-dichlorobenzene, 1,4-dichlorobenzene, 1,3,5-trichlorobenzene, 1-chloronaphthalene).
“…This is consistent with the first-order pyrolysis model proposed by De Vissher et al for monocyclic aromatic compounds (). In addition, products characteristic of the reaction (carbon monoxide, carbon dioxide, acetylene, HCl) are gases obtained experimentally in gas-phase flameless oxidation of chlorobenzene ( , ). 5 4-ClPh, ClBz, and Cl - evolution with time.…”
Propagation of an ultrasonic wave in a water generates the cavitation bubbles, which behaving like microreactors are the center of a high-energy phenomenon leading to destruction of organic pollutants. In this work, a comparative study conducted with chlorobenzene and 4-chlorophenol as models for hydrophobic and hydrophilic substrates, respectively, clearly shows the two sites where the sonochemical reactions can occur. As ultrasonic frequency may alter noticeably the reaction rates, the experiments were conducted at 20 and 500 kHz. The dechlorination yields were found to be higher with the 500-kHz ultrasonic source than with the common 20-kHz probe. For chlorobenzene (ClBz), the reaction proceeds expeditiously, chlorine is quantitatively recovered as chloride ions, and 44% of the carbon atoms are recovered as CO and CO 2 . The rate of disappearance of starting material, Clrelease, and intermediate and final products provide some evidence of a reaction occurring thermally inside the cavitation bubble. 4-Chlorophenol (4-ClPh) degradation occurs at a lower rate. Clrelease and formation of hydroxylated intermediates are evidence of a two-step reaction involving the • OH radical outside the cavitation bubble. The consequences are important for water containing both 4-ClPh (0.5 mM) and ClBz (0.5 mM). ClBz degrades first; 4-ClPh transformation starts only when ClBz concentration reaches a low level (0.02 mM). The sonochemical treatment appears to be particularly efficient for the destruction of volatile chloroaromatic hydrocarbons (1,2-dichlorobenzene, 1,3-dichlorobenzene, 1,4-dichlorobenzene, 1,3,5-trichlorobenzene, 1-chloronaphthalene).
“…In a related study of the gas-phase oxidation of C 6 H 5 Cl, Senkan, Gutman, and co-workers suggested two different mechanisms for phenyl radical decomposition following chlorine atom cleavage . One mechanism is by β-scission of phenyl radical, and the other is a series of reactions after the oxidation of phenyl radical with the following mechanism: This ring-opening mechanism has not been further examined to determine whether it is an energetically viable pathway for the oxidation of benzene.…”
The Gibbs free energy profiles for the unimolecular decomposition of the 2-oxepinoxy radical at temperatures
ranging from 298 to 1250 K have been obtained using the B3LYP method. Intermediates and transition states
have been obtained that link the 2-oxepinoxy radical to various products that have been experimentally observed
during the thermal oxidation of benzene. The pathways explored include the rearrangement of 2-oxepinoxy
radical to cyclopentadienyl radical, pyranyl radical, and various C4, C3, and C2 compounds. The decomposition
of 2-oxepinoxy radical for these pathways provides a mechanism that proceeds from C6 → C5 → C4 → C2
intermediates but does not include the cyclopentadienyl radical as a required intermediate. The most viable
pathway at temperatures between 1000 and 1250 K yields either the 5-oxo-2-cyclopenten-1-yl radical and
CO or the vinyl radical, acetylene, and two molecules of CO as products. A mechanism to form 5-oxo-2-cyclopenten-1-yl, a possible precursor to cyclopentadienone, is compared to the pathway for cyclopentadienone
formation from the decomposition of phenoxy radical to cyclopentadienyl radical and then subsequent oxidation
and rearrangement.
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